Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh hai » thanh hai, nhanh hai, hang hai
sach thu » sach thue, sach thieu, sach tham
cua viet » ca viet, hoa viet, cua vat
thu hanh » thuc hanh, thu thanh, thuy hanh
cac tuc » cac toc, cac tu, cac tac
xa hanh » xa thanh, xa khanh, va hanh
hai cua » thai cua, dai cua, hoi cua
hieu va » lieu va, hieu qua
ca hoi » cau hoi, cua hoi, co hoi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach thu hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (hoc nuoc)) xa hanh hai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thu hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) OR (hoc nuoc)) xa hanh hai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach thu hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (hoc nuoc)) xa hanh hai cua viet".
• Adding a wildcard symbol may retrieve word variants: toc sach thu hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (hoc nuoc)) xa hanh hai cua viet*.